Inhibition by aspirin of release of antiheparin activity from human platelets

Both in vitro and in vivo, aspirin inhibited the adenosine diphosphate and collagen-induced release of platelet factor 4 (antiheparin factor). The release induced by adrenaline and thrombin was not affected. The in-vivo effect in normal persons lasted for at least three days. Platelet uptake of acetyl-(14)C-aspirin was significantly greater than that of carboxyl-(14)C-aspirin.